How Cancer Avoids the Attacking Immune System

A new class of cancer therapies will allow doctors to administer immunotherapy drugs to spur a patient’s own immune system but it doesn’t work with all patients. New research may show the reason that cancers are able to elude these therapies in some patients.

A study focused on colorectal and prostate cancer that was published last week in the journal Cell holds promise in finding answers. These cancers are among those that seem impervious to treatment with immunotherapy drugs. A particular molecule found on the surface of some tumor cells sends a signal that hinders the progress of the immune system. Drug therapies block the signal so that the immune system continues to attack the cancer.

The research indicates that even cancer cells that do not have this molecule on their surface are still using it to trick the immune system. The molecule is being released into the body instead of remaining on the surface of the cancer cell. Immune cells are tricked by the molecule that travels to the lymph nodes and coaxes them to stay put.

Scientists at the University of California, San Francisco have discovered that they can cure a mouse of prostate cancer if they remove those specific molecules that are traveling to the lymph nodes. When the molecules were eliminated, the immune system was able to attack the cancer effectively. The molecules were reintroduced later on into the same mouse, and the immune system was still able to carry out its work. The research was conducted in mice and laboratory experiments and it is not clear if the results will be the same in humans. A paper published last year in the journal Nature showed the same result when the molecules released from skin cancer tumors suppressed immune functions. 


The molecules traveling outside the cell are known as exosomal. The discovery of the role they play in suppressing the immune system is one of the most promising cancer research findings in decades. Countless new studies are underway to refine therapies and search for other molecules implicated in immunosuppression. Preventing these molecules from invading the lymph nodes can contribute to more effective therapies for patients fighting cancer.

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